1. Field of the Invention
The present invention relates to a metal detector for localizing a foreign metal body which has penetrated or has been implanted into a human or animal body.
2. Description of the Related Art
The localization of foreign metal bodies which have penetrated or been implanted into a body frequently causes unforeseen difficulties, e.g., as a result of scarring, bony concretions or a complicated position within the body. For this reason, the localization and the extraction may involve a considerable amount of work and expenditure of time.
Foreign metal bodies are considered to be metal parts which have pentrated into the body or implanted osteosynthesis materials, such as screws, nuts, tension boom wires and cerclage wires, Kirschner's wires and also so-called fixations for epitheses. The foreign metal bodies which have penetrated in this manner must be removed in order to prevent infections or other reactions of the tissue to foreign bodies.
Any implanted foreign metal body should generally be removed after a guaranteed fracture union because the points of proximal contact with the body tissue may corrode and lead to an undesired foreign body irritation, this because the implant causes an elasticity loss of the bone.
In the case of fixations, these fixations have to be localized precisely at the recovery in order to make it possible to secure the so-called epitheses thereto.
Although, for the detection of an implant, the scar of the orignal area of operation is usually circumcised, it is frequently impossible to localize the material by feeling or by means of needles because it is either covered by a scar tissue or callus layer or it may also have moved in rare cases.
According to the prior art, a radiologic representation of the material is made, for example, by means of an X-ray image converter which is slewable through 360.degree.. The disadvantage of this method is the fact that only the horizontal or vertical, i.e. the two-dimensional, position of the material is indicated successively. Consequently, only the position with respect to its width or depth is visible on the X-ray, even though the work is performed on a three-dimensional body.
In difficult cases, the location is usually determined by narrowing down the position of the foreign body by means of needles which are inserted into the tissue, i.e., an approach to the foreign body is carried out by more or less frequent X-ray exposures.
However, this method has the following disadvantages:
The patient and the personnel are exposed to X-ray doses which are not insignificant; PA1 the personnel has to work under aggravated conditions since, because of the radiation exposure, it is compulsory to wear heavy lead rubber aprons; PA1 the search for a foreign metal body causes damage to the tissue; PA1 the removal of the metal may require a relatively large amount of time, so that the patient needs to be narcotized an equally long time, i.e. for long work periods and correspondingly long occupancy periods of operating rooms; PA1 at least two persons are required for removal of the metal namely, an operator and an assistant for operating the X-ray C-arc. PA1 accurate, three-dimensional, quick localization of foreign metal bodies by means of visual displays, PA1 additional localization aid by means of an audible signal, PA1 single-handed operation of the device by one operator; PA1 sensitivity control by the operator by means of a sensitivity sensor integrated into the measuring probe, PA1 simple and proved operation, PA1 optimized probes with different depths of penetration for surgical use in various fields, e.g., general surgery, ENT-surgery, dental surgery, oral surgery and facial surgery, PA1 unrestricted suitability for bone surgery operations, PA1 completely sterilizable: probes, connection cable, plugs are sterilizable in the autoclave together with the surgical instruments; PA1 rugged, easily transportable device.